Search

The textile and dyeing industry have shown dramatic growth alongside synthetic chemistry in the last century. With operations and economic importance, challenges also increase, including environmental pollution, work safety, and consumer health. Change of perspectives in the industry is on the rise, so environmentally-friendly solutions for safer processes and more circularity are urgently sought-after. A possible solution for the pressing issue of textile dyeing is the use of natural colourants obtained in fermentation processes. In this contribution, a comparison between biologically-derived dyes and their synthetic counterparts is conducted on several levels. The structural diversity of biogenic dyes is potentially high enough to pose an alternative on a broad front. Matching fundamental properties concerning dyeing, (bio)synthesis and toxicity give an impression of the advantages of developing this natural alternative. The most important topics for the future are outlined. Major challenges and potential solutions that limit the implementation of biogenic dyes into the textile dyeing value chain are discussed. Biotechnology offers numerous methods to increase reliable production or engineer molecular properties elegantly. The biggest advantage from a Green Chemistry perspective is the possibility to switch to renewable starting materials and obtain more biodegradable dyes. A more sustainable alternative in textile dyeing is afoot. It needs to be embraced and developed to provide the world population with a sustainable way into the future.

Covalent organic frameworks (COFs) have emerged as highly crystalline porous organic materials and proved to be the potential candidates for various interesting applications, such as gas adsorption and separation, catalysis, energy storage, and sensing, etc. Fluorescence-based sensing has gained great attention due to its high selectivity, rapid response time, and real-time monitoring. Lately, luminescent COFs have come to the fore as sensing probes to detect the various target molecules. In this review, we have targeted a comprehensive account of the chronological development of the field of COFs starting from 2005 till date. We have described the design principle with a focus on various topologies reported, classification of their structural diversity on the basis of thirty-two linkages and dimensionality, methods of synthesis with examples, and the use of various characterization techniques. Interestingly, almost one-half of the COFs contains linkages that are nitrogen-rich. With a background in different processes involved for fluorescence sensing, we have illustrated the potential applicability of nitrogen-rich COFs as sensors for numerousanalytes, such as explosives, volatile organic molecules, pH, temperature, toxic anions, metal ions and biomolecules from different media utilizing the striking features of COFs with predesigned structures and diverse functionality.

Two-dimensional metal halide perovskites are being immensely investigated because of the structural diversity and stability offered by this vast family of materials. Many efforts have been devoted to the use of these materials in diverse applications by tuning the optical band gap. The key parameter that needs to be controlled for efficient charge transport in two-dimensional perovskites is the crystal orientation. In this review, we first discuss the mechanisms of crystal formation and crystal growth to obtain the preferred vertical orientation. Next, the impact of organic spacer cations on controlling the growth and crystal orientation of 2D thin films will be discussed based on some of the strategies that allow optimizing these features such as compositional engineering, processing engineering, additive engineering, and the effect of solvent and temperature. At the end, the current challenges and future perspectives are proposed.

Covering: 2000 to 2020. trans-Bicyclo[4.4.0]decane/decene (such as trans-decalin and trans-octalin)-containing natural products display a wide range of structural diversity and frequently exhibit potent and selective antibacterial activities. With one of the major factors in combatting antibiotic resistance being the discovery of novel scaffolds, the efficient construction of these natural products is an attractive pursuit in the development of novel antibiotics. This highlight aims to provide a critical analysis on how the presence of dense architectural and stereochemical complexity necessitated special strategies in the synthetic pursuits of these natural trans-bicyclo[4.4.0]decane/decene antibiotics.

Ba2BS3Cl and Ba5B2S8Cl2 have been synthesized by using PbCl2 as the flux and source of halogen. The two compounds show 3D network structures built by isolated [BS3] units with different Ba–S–Cl groups. This work enriches the structural diversity of boron chemistry and provides an insight into the synthesis of thioborates.

Polyether polyols as a crucial chemical for the synthesis of polyurethanes have attracted much attention, especially for propylene oxide-based polyether polyols due to their ready availability and good structural diversity. In the present work, microreactors configured with a SIMM-V2 micromixer and stainless steel capillary were developed for the continuous and efficient synthesis of propylene oxide-based polyether polyols. For the conversion of propylene oxide higher than 95%, the reaction time was less than 60 s that was significantly shorter than that in a batch reactor. Also, the reaction temperature can be controlled precisely, thereby obtaining high purity polyether polyol products. To identify the maximum performance of the microreactors, while keeping the conversion of PO higher than 95%, the novel process windows of the reactors were determined by investigating the relations of reaction temperature and pressure, reaction temperature and residence time, and feed flow rate and residence time. The results showed that high quality polyether polyols could be easily prepared in the microreactors under flexible operating conditions. In addition, polyether polyols with higher molecular weights could also be prepared by using a two SIMM-V2 configured microreactor. This work showed that the microreactors are promising candidates for the synthesis of polyether polyols in the industry.

Organozinc hydrazides have gained considerable interest in current research for their significant applications as single source molecular precursors in chemical science as well as their versatile structural diversity. Various hydrazide derivatives are normally prepared from a ‘one-pot’ synthesis protocol by reacting dialkylzinc and hydrazine in the presence of secondary ligands at an appropriate ratio, and the reaction proceeds via successful replacement of one or more hydrazide units by secondary ligands through alkane elimination. Due to the polydentate binding nature of the N–N moiety of the hydrazine ligand, these organozinc hydrazides adopt a great variety of structures such as four-membered heterocycles, polycyclic frameworks and cages. The hydrogen storage properties of selected hydrazides and their derivatives are also discussed in this review.

Galectins are potential biomarkers and therapeutic targets. However, galectins display broad affinity towards β-galactosides meaning glycan-based (nano)biosensors lack the required selectivity and affinity. Using a polymer-stabilized nanoparticle biosensing platform, we herein demonstrate that the specificity of immobilised lacto-N-biose towards galectins can be ‘turned on/off’ by using site-specific glycan fluorination and in some cases reversal of specificity can be achieved. The panel of fluoro-glycans were obtained by a chemoenzymatic approach, exploiting BiGalK and BiGalHexNAcP enzymes from Bifidobacterium infantis which are shown to tolerate fluorinated glycans, introducing structural diversity which would be very laborious by chemical methods alone. These results demonstrate that integrating non-natural, fluorinated glycans into nanomaterials can encode unprecedented selectivity with potential applications in biosensing., A chemo-enzymatic site-specific fluorination strategy is employed to obtain glyco-nanoparticles with tuneable selectivity towards galectins.

A Ni-catalyzed direct C–H alkylation of N-quinolylbenzamides using alkylsilyl peroxides as alkyl-radical precursors is described. The reaction forms a new C(sp3)–C(sp2) bond via the selective cleavage of both C(sp3)–C(sp3) and C(sp2)–H bonds. This transformation shows a high functional-group tolerance and, due to the structural diversity of alkylsilyl peroxides, a wide range of alkyl chains including functional groups and complex structures can be introduced at the ortho-position of readily available N-quinolylbenzamide derivatives. Mechanistic studies suggest that the reaction involves a radical mechanism.

Covering: up to 1 October 2020 Solanum steroidal glycoalkaloids (SGA), characterized by nitrogenous steroidal aglycone and glycoside residues, mainly occur in the Solanum species, including economically important edible plants such as potato, tomato, and eggplant. To date, 107 SGA assigned to six total skeletons have been identified from Solanum plants. SGA have unique structures and display significant pharmacological activities such as cytotoxic, antimicrobial, anticholesterol, and some are well-known poisons. The biosynthesis pathway, transcriptional regulation, and the evolution of SGA are also examined in detail. This report updates the chemical knowledge of the naturally occurring SGA from Solanum species, thereby providing an in-depth analysis of their diversity, biological activities, and biosynthesis.

Lithium–sulfur (Li–S) batteries have emerged as promising energy storage devices due to their high theoretical specific energy densities; their practical applications, however, have been restricted due to their poor cycling stability arising from the shuttle effect of the S cathode and dangerous Li dendrite growth. S and Li can be encapsulated into porous framework hosts to address these issues. Metal–organic frameworks (MOFs)/covalent-organic frameworks (COFs) have shown great potential due to their tunable frameworks, structural diversity, and functional versatility. In this review, the applications of MOFs/COFs for Li–S batteries in terms of the sulfur hosts, electrolyte containers, separators, and Li dendrite blocking barriers are systematically summarized. A short conclusion and outlook regarding future research opportunities for pristine MOFs/COFs for Li–S batteries are also provided.

An efficient method to synthesize diaryl sulfides with structural diversity is disclosed. Demethylative hydrothiolation of aryne intermediates generated from o-iodoaryl triflates with methylthio-substituted o-silylaryl triflates and further aryne reactions afford diverse diaryl sulfides.

Applications of phthalocyanines (Pcs) in electrocatalysis—including the oxygen reduction reaction (ORR), the carbon dioxide reduction reaction (CO2RR), the oxygen evolution reaction (OER), and the hydrogen evolution reaction (HER)—have attracted considerable attention recently. Pcs and their derivatives are more attractive than many other macrocycles as electrocatalysts since, although they are structurally related to natural porphyrin complexes, they offer the advantages of low cost, facile synthesis and good chemical stability. Moreover, their high tailorability and structural diversity mean Pcs have great potential for application in electrochemical devices. Here we review the structure and composition of Pcs, methods of synthesis of Pcs and their analogues, as well as applications of Pc-based heterogeneous electrocatalysts. Optimization strategies for Pc-based materials for electrocatalysis of ORR, CO2RR, OER and HER are proposed, based on the mechanisms of the different electrochemical reactions. We also discuss the structure/composition–catalytic activity relationships for different Pc materials and Pc-based electrocatalysts in order to identify future practical applications. Finally, future opportunities and challenges in the use of molecular Pcs and Pc derivatives as electrocatalysts are discussed.

The direct use structurally simple ketones as α-ketone radical sources for α-C(sp3)–H functionalization is a sustainable and powerful approach for constructing complex and multifunctional chemical scaffolds with diverse applications. The reactions of α-ketone radicals with alkenes, alkynes, enynes, imides, and imidazo[1,2-a]pyridines have broadened the structural diversity and complexity of ketones. Through chosen illustrative examples, we outline the recent progress in the development of methods that enable the radical α-C(sp3)–H functionalization of ketones, with an emphasis on radical initiation systems and possible mechanisms of the transformations. The application of these strategies is illustrated by the synthesis of several biologically active molecules and drug molecules. Further subdivision is based on substrate type and reaction type.

Current commercial batteries cannot meet the requirements of next-generation technologies, meaning that the creation of new high-performance batteries at low cost is essential for the electrification of transport and large-scale energy storage. Solid-state batteries are being widely anticipated to lead to a step improvement in the performance and safety of batteries and their success is heavily dependent on the discovery, design and optimisation of the solid electrolytes that they are based on. In recent years, Li- and Na-rich anti-perovskite solid electrolytes have risen to become highly promising candidate materials for solid-state batteries on the basis of their high ionic conductivity, wide electrochemical window, stability, low cost and structural diversity. This perspective highlights experimental and atomistic modelling progress currently being made for Li- and Na-rich anti-perovskite solid electrolytes. We focus on several critical areas of interest in these materials, including synthesisability, structure, ion transport mechanisms, anion rotation, interfaces and their compatibility with anti-perovskite cathodes for the possible formation of anti-perovskite electrolyte- and cathode-based solid-state batteries. The opportunities and challenges for the design and utilisation of these materials in state-of-the-art solid-state batteries are also discussed. As featured throughout this perspective, the versatility, diversity and performance of anti-perovskite solid electrolytes make them one of the most important materials families currently under consideration for solid-state batteries.

A new heavy metal oxychloride, RbPb8O4Cl9, has been synthesized by a high-temperature solution method. The compound crystallizes in the centrosymmetric space group P4/n (no. 85) and exhibits a three-dimensional (3D) framework constructed from [PbO3Cl3], [PbOCl5] and [RbCl8] polyhedra. RbPb8O4Cl9 is an indirect band gap compound with an experimental band gap of 3.66 eV. The first-principles calculations indicate that the band gap mainly originated from the interaction of Pb 6p, O 2p and Cl 2p states. Meanwhile, the calculated birefringence of RbPb8O4Cl9 is about 0.012 at 1064 nm. The compound is the first alkali metal lead oxyhalide, which enriches the structural diversity of oxyhalides and provides an insight for the exploration of new functional materials.

Ionic liquids (ILs) have been labeled as a promising green alternative to traditional materials; however, many ILs have been discovered to be toxic, especially hydrophobic ILs (HILs). HILs are limited in their structural diversity as most are composed of heteroaromatic cations with long alkyl chains and paired with [BF4], [PF6], or [NTf2] anions. This study aims to diversify HILs by synthesizing two sets of HILs with unique cations and anions. The first set of HILs contain cholinium- and dicholinium-based cations paired with the [NTf2] anion. The [DC-ether] cation is identified as a promising cation and is paired with an array of asymmetric bis(sulfonyl)amide anions to form the second set of HILs. In total, twenty HILs are synthesized. Each HIL is characterized using traditional physicochemical techniques and is evaluted for toxicity using in vitro and in vivo methods.

Simultaneous deconstructive ring-opening and skeletal reconstruction of an inert, aromatic pyridinium ring is of great importance in synthetic communities. However, research in this area is still in its infancy. Here, a skeletal re-modeling strategy was developed to transform chalcone-based pyridinium salts into structurally intriguing polycyclic isoindolines through a dearomative ring-opening/ring-closing sequence. Two distinct driving forces for the deconstruction of the pyridinium core were involved in these transformations. One was the unprecedented harnessing of the instability of in situ generated cyclic β-aminoketones, and the other was the instability of the resultant N,N-ketals. The desired isoindoline polycycles could undergo the Wittig reaction with various phosphorus ylides to achieve structural diversity and complexity. Notably, by tuning the Wittig conditions by addition of one equivalent of base, an additional bridged ring was introduced. A plausible mechanism was proposed on the basis of control experiments and theoretical calculations., A novel skeletal remodeling strategy to transform chalcone-based pyridinium salts into structurally intriguing polycyclic isoindolines was achieved through a dearomative ring-opening/ring-closing sequence.

Na-ion batteries (NIBs) are promising alternatives to Li-ion batteries (LIBs) due to the low cost, abundance, and high sustainability of sodium resources. However, the high performance of inorganic electrode materials in LIBs does not extend to NIBs because of the larger ion size of Na+ than Li+ and more complicated electrochemistry. Therefore, it is vital to search for high-performance electrode materials for NIBs. Organic electrode materials (OEMs) with the advantages of high structural tunability and abundant structural diversity show great promise in developing high-performance NIBs. To achieve advanced OEMs for NIBs, a fundamental understanding of the structure–performance correlation is desired for rational structure design and performance optimization. In this review, recent advances in developing OEMs for non-aqueous, aqueous, and all-solid-state NIBs are presented. The challenges, advantages, mechanisms, development, and applications of advanced OEMs in NIBs are also discussed. Perspectives for the innovation of structure design principle and future research direction of OEMs in non-aqueous, aqueous, and all-solid-state NIBs are provided.

Gas therapy as a burgeoning and promising research field has attracted considerable attention in biomedicine due to its high therapeutic efficacy, biocompatibility, and biosafety. However, the lack of tumor site accumulation and controlled release of therapeutic gas molecules limited the therapeutic efficacy. Therefore, the development of gas-releasing nanoplatforms to realize tumor targeting and controllable release is highly desired. The structural diversity and tailorability and ultrahigh surface area make metal-organic frameworks (MOFs) find potential applications in the delivery and release of gas or gas releasing molecules (GRMs). In this Frontier article, we provide an overview of the recent developments achieved in gas-involving cancer therapy using MOFs or MOF-based materials. The main emphasis is focused on the design of multifunctional MOF-based nanoplatforms for the delivery and release of therapeutic gas molecules, and emphasizing their synergistic mechanism against tumor. Moreover, the challenges, future trends, and prospects of gas-related cancer therapy are also discussed.

Photoactive MOF-based delivery systems are highly attractive for photodynamic therapy (PDT), but the fundamental interplay among structural parameters and photoactivity and biological properties of these MOFs remains unclear. Herein, porphyrinic MOF isomers (TCPP-MOFs), constructing using the same building blocks into distinct topologies, have been selected as ideal models to understand this problem. Both the intramolecular distances and molecular polarization within TCPP-MOFs isomers collectively contribute to the photoactivity of generating reactive oxygen species. Remarkably, the morphology-determined endocytic pathways and cytotoxicity, as well as good biocompatibility have been confirmed for TCPP-MOF isomers without any chemical modification for the first time. Besides the topology-dependent photoactive regulation, this work also provides in-depth insights into the biological effect from the MOF nanoparticles with controllable structural factors, benefiting further in vivo applications and clinical transformation.

The significance of H2O2 in biological systems and its wide application in various areas, such as municipal wastewater treatment, aseptic packaging, etc., have enabled the development of simple, stable, and highly sensitive H2O2 sensors that have gained growing research interest. With the fast development of nanotechnology, the emergence of enzyme-free electrochemical H2O2 sensors based on efficient enzyme-mimetic electrocatalysts has opened up new horizons for researchers. Among them, carbon nanomaterials stand out from many nanomaterials with enzyme-like electrocatalytic activity due to their remarkable structural diversity, considerable cost-effectiveness, as well as fascinating and stable physicochemical properties. Importantly, carbon nanomaterials can act as nano-supports for other electrocatalysts in addition to being directly used as electrocatalysts. Moreover, the carbon hybrid nanocomposites tend to be superior to each component in electrochemical performance due to synergistic effects. Therefore, carbon hybrid nanocomposites are emerging as promising materials for highly efficient and sensitive enzyme-free electrochemical H2O2 detection. In this review, we overview the recent advances of carbon hybrid nanocomposites in enzyme-free electrochemical H2O2 sensing, covering the characteristics and performance of various carbon hybrid nanocomposites based on other electrocatalysts hybridized with carbon nanomaterials and the optimized design of carbon hybrid nanocomposites in improving the enzyme-free electrochemical detection of H2O2.

The structures of seven compounds based on guanidinium cations, isolated sulfate anions, and additional organic cations and solvent molecules are reported. All seven compounds, (C(NH2)3)2(SO4) (1), (C(NH2)3)3(C5H6N)(SO4)2 (2), (C(NH2)3)3(C5H6N)(SO4)2·H2O (3), (C(NH2)3)3(C5H6N)(SO4)2·CH3OH (4), (C(NH2)3)11(C5H6N)(SO4)6·2.5C2H5OH (5), (C(NH2)3)3(C6H16N)(SO4)2 (6), and (C(NH2)3)2(C20H26N2O2)(SO4)2 (7) crystallize without a center of symmetry, and are built of related motifs of six-membered rings via hydrogen bonding of three guanidinium cations and three sulfate anions. These six-membered rings form extended sheets and frameworks through additional hydrogen bonding interactions. The presence of additional cations and solvent molecules in varying ratios add structural diversity by modifying the guanidinium sulfate frameworks, but retaining the acentricity of the structures. The study reveals a remarkable tendency for these guanidinium sulfate frameworks to crystallize without a center of symmetry, and furthermore, in polar or chiral space groups. This provides a potential pathway for the use of hydrogen bonding interactions to design structures having interesting physical or nonlinear optical properties.

Using asymmetric 2-chloro-4-ferrocenylbenzoic acid, six new complexes formulated as {[Mn(OOCClH3C6Fc)2(H2O)3]·(CH3OH)}n (1), {[Ni(OOCClH3C6Fc)2(H2O)3](CH3OH)}n (2), [Co(OOCClH3C6Fc)2(H2O)3]n (3), [Co(η2-OOCClH3C6Fc)(fcz)]2·CH3OH (4) [Hfcz = a-(2,4-difluorophenyl)-a-(1H-1,2,4,-triazol-1-ylmethyl)-1H-1,2,4-triazole-1-ethanol], [Ni(η2-OOCClH3C6Fc)(fcz)]2·2CH3OH (5), and [Mn(OOCClH3C6Fc)2(phen)(H2O)] (6) [phen = 1,10-phenanthroline monohydrate] have been synthesized and structurally characterized. 1–3 are isostructural and display 1D aqua-bridged chain structures, in which 1–3 reveal antiferromagnetic coupling with J = −2.35 cm−1 for 1, J = −25.92 cm−1 for 2 and J = −3.98 cm−1 for 3. Notably, 2 and 3 with 1D μ2-aqua bridges haven't been reported before. Complexes 4 and 5 show dinuclear hydroxyl-bridged structures, in which 4 also exhibits antiferromagnetic coupling with J = −2.46 cm−1. For 6 with a 1D carboxyl-bridged chain structure, it also exhibits antiferromagnetic behaviour with J = −1.11 cm−1.

The wide availability and low cost of potassium resources have made electrochemical potassium storage a promising energy storage solution for sustainable decarbonisation. Research activities have been rapidly increasing in the last few years to investigate various potassium batteries such as K-ion batteries (KIBs), K–S batteries and K–Se batteries. The electrode materials of these battery technologies are being extensively studied to examine their suitability and performance, and the utilisation of hybrid nanostructures has undoubtedly contributed to the advancement of the performance. This review presents a timely summary of utilising hybrid nanostructures as battery electrodes to address the issues currently existing in potassium batteries via taking advantage of the compositional and structural diversity of hybrid nanostructures. The complex challenges in KIBs and K–S and K–Se batteries are outlined and the role of hybrid nanostructures is discussed in detail regarding the characteristics of intercalation, conversion and alloying reactions that take place to electrochemically store K in hybrid nanostructures, highlighting their multifunctionality in addressing the challenges. Finally, outlooks are given to stimulate new ideas and insights into the future development of hybrid nanostructures for electrochemical potassium storage.

Atomically precise silver nanoclusters with ultrasmall sizes (

Reticular chemistry of covalent organic frameworks (COFs) deals with the linking of discrete organic molecular building units into extended structures adopting various topologies by strong covalent bonds. The past decade has witnessed a rapid development of COF chemistry in terms of both structural diversity and applications. From the structural perspective, irrespective of our subject of concern with regard to COFs, it is inevitable to take into account the structural aspects of COFs in all dimensions from 1D ribbons to 3D frameworks, for which understanding the concepts of reticular chemistry, based mainly on ‘reticular design’, will seemingly lead to unlimited ways of exploring the exquisiteness of this advanced class of porous, extended, and crystalline materials. A comprehensive discussion and understanding of reticular design, therefore, is of paramount importance so that everyone willing to research on COFs can interpret well and chemically correlate the geometrical structures of this subset of reticular materials and their practical applications. This article lies at the heart of using the conceptual basis of reticular chemistry for designing, modeling, and determination of novel infinite and crystalline structures. Especially, the structure determinations are described by means of chronological advances of discoveries and development of COFs whereby their crystal structures are elucidated by modeling through the topological approach, 3D electron diffraction, single-crystal X-ray diffraction, and powder X-ray diffraction techniques., This article describes the conceptual basis of rational design in COF chemistry and comprehensively discusses the crystal structure determination of COFs using the topological approach, X-ray diffraction, and 3D electron diffraction.

The first alkali-earth metal lead(II) oxyhalide Ba8SrPb24O24Cl18 characterized by fascinating multimember-ring layers has been discovered. Theoretical and experimental investigations illustrate that Ba8SrPb24O24Cl18 exhibits a moderate band gap of 3.09 eV, incongruent melting behavior and birefringence of 0.014@1064 nm. This discovery may offer new ideas for regulating the optical properties of oxyhalides and broadening their structural diversity.

A Brønsted acid-catalyzed C3-alkylation of indolizines has been established with different electrophiles such as ortho-hydroxybenzyl alcohols, other precursors of para-quinone methides and ortho-quinone methides, and 2-indolylmethanol as well. By using this approach, a series of C3-functionalized indolizines were synthesized in overall good yields (up to 89%). These examples demonstrate that the Brønsted acid-catalyzed C3-alkylation of indolizines has a wide applicability, which can serve as a useful method for synthesizing C3-functionalized indolizine derivatives with structural diversity. This reaction has fulfilled the task of developing organocatalytic C3-functionalization of indolizines for the synthesis of biologically important indolizine derivatives.

Three Co(II) coordination polymers (CPs), {[Co2(HL)(1,4-bibb)(H2O)]·(CH3CN)·(H2O)}n (1), {[Co4(L)(OH)3(H2O)4]·(1,4-bmib)}n (2) and {[Co6(L)2(OH)2(4,4-biyb)]·(CH3CN)·(H2O)}n (3) have been obtained based on a V-shaped rigid pentacarboxylate ligand (H5L = 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid) and different N-donor ligands. All complexes show 3D structures and contain open carboxyl sites and “accessible metal sites” (AMSs). The gas adsorption experiments show that 1 and 3 have a high H2 adsorption capacity at 77 K and in particular, 3 displays the selective uptake of CO2 over CH4 (14.2 for CO2/CH4 = 0.5/0.5 and 11.0 for CO2/CH4 = 0.05/0.95 under 1 bar at 298 K). Furthermore, anti-ferromagnetic interactions among Co(II) ions are observed in 2.

Structurally ordered intermetallic borides are a large family of inorganic solids with rich bonding schemes, and huge compositional and structural diversity. The family members possess high flexibility to modulate the local electronic structures and surface adsorption properties, providing great opportunities for the development of advanced catalysts with superior activity and stability. In this review, we summarize the structural features of intermetallic borides, with emphasis on the covalent linkage patterns of boron atoms in them, and the research methods for understanding their electronic structures. We also present the recent developments in the synthesis of phase-pure, well-defined intermetallic borides, most of which are suitable for catalytic studies. We further highlight the theoretical and experimental advances in the emerging boride-catalyzed reactions and the important roles of boron in tuning electrocatalytic performances. Finally, we propose the remaining challenges and future developments of boride synthesis and catalytic applications.

Covering: up to 2019 There is significant demand for new aminoglycoside antibiotics due to the widespread emergence of multidrug-resistant Gram-negative bacteria and their high toxicity, but these are not easily accessible in nature because their biosynthetic gene clusters are less commonly found in actinomycetes than are other natural products. Mining minor aminoglycoside components whose pharmacological activity has not yet been assessed could be an alternative approach for the development of next-generation antibiotics for use in the post-antibiotic era. Here, we review the biosynthetic steps responsible for the structural diversity of aminoglycosides and highlight current developments regarding the use of natural minor and semi-synthetic aminoglycosides as promising therapeutic leads or candidates.

An innovative strategy based on dual structure-directing agent-facilitated crystallization was proposed to hydrothermally synthesize boron-free Zr-MWW and Sn-MWW metallosilicates that bear great structural diversity for potential pore engineering. The metallosilicates show distinctive features in Lewis acid-catalyzed reactions as efficient heterogeneous solid catalysts.

Due to the low cost and abundance of multivalent metallic resources (Mg/Al/Zn/Ca), multivalent rechargeable batteries (MRBs) are promising alternatives to Li-ion and Pb-acid batteries for grid-scale stationary energy storage applications. However, the high performance of inorganic electrode materials in Li-ion batteries does not extend to MRBs, because the high charge density of multivalent cations dramatically reduces their diffusivity in the crystal lattice of inorganic materials. To achieve high-performance MRBs, organic electrode materials (OEMs) with abundant structural diversity and high structural tunability offer opportunities. This review presents an overview of the state-of-the-art OEMs in MRBs, including non-aqueous rechargeable Mg/Al/Zn and aqueous rechargeable Mg/Al/Zn/Ca batteries. The advantages, challenges, development, mechanism, structure, and performance of OEMs in MRBs are discussed in detail. To provide a comprehensive and thorough understanding of OEMs in MRBs, the correlation between molecular structure and electrochemical behavior is also summarized and discussed. This review offers insights for the rational structure design and performance optimization of advanced OEMs in MRBs.

The reversible reaction of CO2 with alcohols in the presence of organic bases was successfully developed to be a toolbox for capturing CO2 into polymerizable α,ω-diene functionalized carbonate monomers with high structural diversity. These are applicable for thiol–ene click and ADMET polymerization to produce new libraries of poly(thioether carbonates) and unsaturated aromatic–aliphatic polycarbonates with high molecular weights and satisfactory thermal properties.

Covering: 2009 to 2018. Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, are a diverse class of compounds having complex structural features with many stereocenters. The important pharmacological activities and structural complexity of the diterpenoid alkaloids have long interested scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. Since 2009, 373 diterpenoid alkaloids, assigned to 46 skeletons, have been isolated and identified from plants mostly in the Ranunculaceae family. The names, classes, molecular weight, molecular formula, NMR data, and plant sources of these diterpene alkaloids are collated here. This review will be a detailed update of the naturally occurring diterpene alkaloids reported from the plant kingdom from 2009-2018, providing an in-depth discussion of their diversity, biological activities, pharmacokinetics, toxicity, application, evolution, and biosynthesis.

The microenvironment within self-assembled supramolecular coordination cages (SCCs) inaugurates a new phase of chemistry other than the conventional solid, liquid and gaseous phases. The rational design and ease of synthesis of self-assembled architectures have received tremendous attention mainly in the field of supramolecular chemistry. The structural transition from 2-D metallacycles to 3-D metallacages has led to better encapsulation and enhanced cavity effects, like restricted substrate motion, desolvation of the substrate and covalent binding of the transition state etc. Metal-mediated self-assemblies, principally known as metallo-supramolecular coordination cages (MSCCs), form a separate class of SCCs with unique chemical phenomena inside the cavities. The aesthetic structural diversity of MSCCs obtained from the rational choice of metal knots and organic linkers renders designable and programmable architectures. This review presents cavity-based applications of these MSCCs, such as molecular recognition and separation, stabilization of reactive species by encapsulation, as drug-delivery systems and as “molecular flasks” to foster reactions with unprecedented results. The objective of this review is to inspire and pave the way for researchers working in this field to design more advanced MSCCs and gain deep insight into cavity effects.

Methods for direct functionalization of C–H bonds mediated by N-oxyl radicals constitute a powerful tool in modern organic synthesis. While several N-oxyl radicals have been developed to date, the lack of structural diversity for these species has hampered further progress in this field. Here we designed a novel class of N-oxyl radicals based on N-hydroxybenzimidazole, and applied them to the direct C–H functionalization reactions. The flexibly modifiable features of these structures enabled facile tuning of their catalytic performance. Moreover, with these organoradicals, we have developed a metal-free approach for the synthesis of acyl fluorides via direct C–H fluorination of aldehydes under mild conditions.

The use of functional groups as internal ligands for assisting C-H functionalization, termed the chelation assisted strategy, is emerging as one of the most powerful tools for construction of C-C and C-X bonds from inert C-H bonds. However, there are various directing groups which cannot be either removed after functionalization or require some additional steps or reagents for their removal, thereby limiting the scope of structural diversity of the products, and the step and atom economy of the system. These limitations are overcome by the use of the traceless directing group (TDG) strategy wherein functionalization of the substrate and removal of the directing group can be carried out in a one pot fashion. Traceless directing groups serve as the most ideal chelation assisted strategy with a high degree of reactivity and selectivity without any requirement for additional steps for their removal. The present review overviews the use of various functional groups such as carboxylic acids, aldehydes, N-oxides, nitrones, N-nitroso amines, amides, sulfoxonium ylides and silicon tethered directing groups for assisting transition metal catalyzed C-H functionalization reactions in the last decade.

Lone pair activity is an important factor to regulate the crystal structure symmetry and related optical response. Herein, a new type of hydrated bismuth fluoride, BiF3·H2O, was synthesized and characterized by a facile hydrothermal reaction. Obviously, the introduction of a water molecule significantly changed the coordination environment of Bi3+, thereby seriously changing the crystal structure of the compound BiF3. Compared with asymmetric BiFm fundamental building blocks in other compounds, BiF3·H2O possesses unprecedented near-isotropic BiF9 polyhedra and exhibits regulated birefringence values. Therefore, this work will contribute to the structural diversity of BimFn-based compounds and explore the development of new birefringent crystals.

Covering: up to July 2019 Terpene synthases (TSs) are responsible for generating much of the structural diversity found in the superfamily of terpenoid natural products. These elegant enzymes mediate complex carbocation-based cyclization and rearrangement cascades with a variety of electron-rich linear and cyclic substrates. For decades, two main classes of TSs, divided by how they generate the reaction-triggering initial carbocation, have dominated the field of terpene enzymology. Recently, several novel and unconventional TSs that perform TS-like reactions but do not resemble canonical TSs in sequence or structure have been discovered. In this review, we identify 12 families of non-canonical TSs and examine their sequences, structures, functions, and proposed mechanisms. Nature provides a wide diversity of enzymes, including prenyltransferases, methyltransferases, P450s, and NAD+-dependent dehydrogenases, as well as completely new enzymes, that utilize distinctive reaction mechanisms for TS chemistry. These unique non-canonical TSs provide immense opportunities to understand how nature evolved different tools for terpene biosynthesis by structural and mechanistic characterization while affording new probes for the discovery of novel terpenoid natural products and gene clusters via genome mining. With every new discovery, the dualistic paradigm of TSs is contradicted and the field of terpene chemistry and enzymology continues to expand.

The root, stem and leaf of Celastrus orbiculatus Thunb. (COT) have all been used as Chinese folk medicine. Aiming at revealing the secondary metabolites and screening the anti-COPD effect of COT, the comprehensive phytochemical and bioassay studies were performed. Based on the ultra-high performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MSE), the screening analysis of components in COT was conducted with the UNIFI platform, the metabolomics of the three parts were analyzed with multivariate statistical analysis. Cigarette smoke extract (CSE)-stimulated inflammatory model in A549 cells was used to investigate the biological effect of the three parts. A total of 120 compounds were identified or tentatively characterized from COT. Metabolomics analysis showed that the three parts of COT were differentiated, and there were 13, 8 and 5 potential chemical markers discovered from root, stem and leaf, respectively. Five robust chemical markers with high responses could be used for further quality control in different parts of COT. The root, stem and leaf of COT could evidently reduce the levels of pro-inflammatory factors in a dose-dependent way within a certain concentration range. The stem part had a stronger anti-COPD effect than root and leaf parts. This study clarified the structural diversity of secondary metabolites and the various patterns in different parts of COT, and provided a theoretical basis for further utilization and development of COT.

The discovery of compounds with novel topologies is likely to extend structural diversity and trigger intriguing physical properties. Herein, the interesting [Pb4Ba4O4]8+ species has been discovered in alkali-earth metal lead(II) oxyhalide Ba27Pb8O8Cl54. Besides, the crystal structures, infrared/Raman spectroscopy, UV-Vis-NIR diffuse reflectance spectroscopy and electronic band structures of Ba27Pb8O8Cl54 have been studied.

Generating samples of nanoparticles with specific properties that allow for structural diversity, rather than requiring structural precision, is a more sustainable prospect for industry, where samples need to be both targeted to specific applications and cost effective. This can be better enabled by defining classes of nanoparticles and characterising the properties of the class as a whole. In this study, we use machine learning to predict the different classes of diamond nanoparticles based entirely on the structural features and explore the populations of these classes in terms of the size, shape, speciation and charge transfer properties. We identify 9 different types of diamond nanoparticles based on their similarity in 17 dimensions and, contrary to conventional wisdom, find that the fraction of sp2 or sp3 hybridized atoms are not strong determinants, and that the classes are only weakly related to size. Each class has been describe in such way as to enable rapid assignment using microanalysis techniques.

We present a series of six novel Zn(II) complexes containing anions of perfluorinated biphenyl-4,4′-dicarboxylate (oFBPDC2−). Among them are the 0D complex [Zn(eg)3](oFBPDC) (eg = ethylene glycol), the 1D [Zn(H2O)(ur)(oFBPDC)] (ur = urotropine) and [Zn(CH3OH)2(CH3OCH2CH2OH)(oFBPDC)] and the 2D layered [Zn2(CH3CN)2(oFBPDC)2]·2C6H6·2CH3CN, [Zn2(H2O)2(oFBPDC)2]·4(CH3)2CO, [{Zn4(μ3-OCH3)4}(CH3OH)4(oFBPDC)2]·[{Zn4(μ3-OCH3)4}(H2O)(CH3OH)3(oFBPDC)2]·13CH3OH. The latter coordination polymer is built up by unique Zn4(OCH3)4 cuboidal units. The complexes are characterized by single-crystal X-ray diffraction, FT-IR, elemental analysis, and TGA. Investigation of the CO2 adsorption at 195 K on [Zn2(CH3CN)2(oFBPDC)2] and [Zn2(H2O)2(oFBPDC)2] of the layered polymeric structure revealed that they have BET surface areas of 334.8 and 150.6 m2 g−1, respectively.

A novel cascade click/nucleophilic substitution reaction is developed to access 4-heterofunctionalized fully substituted triazolyl-organosulfurs using thiocyanates as both leaving groups and organosulfur precursors. This method features high regioselectivities and board substrate scope. 33 examples are shown to demonstrate the structural diversity through the synthesis of fully substituted triazolyl-organosulfurs including triazolyl-thiocyanates, triazolyl-sulfinylcyanides, triazolyl-thioethers, triazolyl-thiols and triazolyl-disulfides from internal thiocyanatoalkynes.

Dye-sensitized solar cells (DSSCs) are the third generation of photovoltaic cells developed by Grätzel and O'Regan. They have the characteristics of low cost, simple manufacturing process, tunable optical properties, and higher photoelectric conversion efficiency (PCE). With an ever increasing energy crisis, there is an urgent need to develop highly efficient, environmentally benign, and energy-saving cell materials. Polyoxometalates (POMs), a kind of molecular inorganic quasi-semiconductor, are promising candidates for use in different parts of DSSCs due to their excellent photosensitivity, redox, and catalytic properties, as well as their relative stability. Following a brief introduction to the development of DSSCs and the potential virtues of POMs in DSSCs, we attempt to make some generalizations about the energy level regulation of POMs that is the underlying theoretical basis for their application in DSSCs, and then we summarize the research progress of POMs in DSSCs in recent years. This is organized in terms of the properties of POMs, namely, electron acceptor, photosensitivity, redox and catalysis, based on the accumulation of our research into POMs over many years. Meanwhile, in view of the fact that the properties of POMs depend primarily on their electronic structural diversity, we keep this point in mind throughout the article with a view to revealing their structure-property relationships. Finally we provide a short summary and remarks on the future outlook. This review may be of interest to synthetic chemists devoted to designing POMs with specific structures, and researchers engaged in the extension of POMs to photoelectric materials.

An analysis of known synthetic methods for dibenzoylmethanide (dbm−) complexes of lanthanides of different nuclearity, viz. [Ln(dbm)3(H2O)], [Ln4(dbm)10(OH)2], [Ln5(dbm)10(OH)5] and [KLn(dbm)4]n (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) has been carried out. These methods have been optimized, the range of lanthanides for the compounds extended, and novel complex species, viz. [KLn(Me2CO)(dbm)4]2 (Ln = Eu, Dy, Yb) and [Nd3(dbm)8(OH)(H2O)], have been produced. The nature of the lanthanides in some cases affects the composition of the products formed. The compound [KEu(Me2CO)(dbm)4]2 in solution can transform to [KEu(dbm)3(OBz)]n, containing benzoate (OBz−). For the seven new complexes, the crystal structures have been determined by X-ray diffraction. Photoluminescent properties of the europium complexes have been studied. Their composition and structure influence the emission band shape and quantum yields. Two solid solutions of heterolanthanide complexes [ErxYb5–x(dbm)10(OH)5] (x = 1.2, 2.0) have been prepared, as shown by high-resolution powder XRD analysis.

Multicomponent reactions (MCRs) include several aspects of green chemistry principles, so it is obvious that chemists in different areas are increasingly interested in providing their product by multicomponent approaches. MCRs can be very useful in supramolecular chemistry, especially to produce novel supramolecular derivatives. Therefore, there are several reports of highly-functionalized calix[4]arene derivatives obtained by MCRs instead of conventional stepwise protocols during the last decade. In this paper, we have particularly focused on the exploitation of upper rim and lower rim substituted calix[4]arenes in multicomponent approaches as a facile and convenient synthetic strategy. The value of this method lies in its operational simplicity, mild reaction conditions and structural diversity of the products. Interestingly, in most cases the products afforded by this method offer unique features and applications which are highlighted in the following sections.

Zwitterionic polymers, including polyampholytes and polybetaines, are polymers with both positive and negative charges incorporated into their structure. They are a unique class of smart materials with great potential in a broad range of applications in nanotechnology, biomaterials science, nanomedicine and healthcare, as additives for bulk construction materials and crude oil, and in water remediation. In this Tutorial Review, we aim to highlight their structural diversity and design criteria, and their preparation using modern techniques. Their behavior, both in solution and at surfaces, will be examined under a range of environmental conditions. Finally, we will exemplify how their unique behaviors give rise to specific properties tailored to a selection of their numerous applications.